With the rapid development of semiconductor manufacturing technology, the semiconductor device has been developed toward higher component density and higher integration degree. To improve the integration degree, the density of transistors continues to increase and the spacing there-between is gradually reduced.
The development of semiconductor device toward high integration degree is often accompanied by a reduction of channel carrier mobility. A conventional solution includes use of strained silicon technologies to improve the channel carrier mobility of the transistor. In the strained silicon technology, a layer of a crystal having a lattice constant different from that of the silicon substrate is epitaxially grown on source and drain regions of the transistor. Moreover, to connect the source and drain regions to external circuits, metal silicide needs to be formed on the layer of the crystal.
However, the performance of conventional semiconductor structure still needs to be improved. The disclosed device structures and methods are directed to solve one or more problems set forth above and other problems.